This invention has relation to an exercise device for exercising the abdominal muscles and the lower back muscles without putting undue stress on the lumbar and cervical spinal discs and without over-exercising the hip flexor muscles.
"It has long been known that sit-up type exercises are beneficial to the abdominal area. However, it is now known that the standard sit-up exercise consisting of raising the trunk to a sitting position from a supine position with the legs remaining straight causes undue stress and trauma to the lower back regions." See U.S. Pat. No. 4,902,003 granted to Buoni on Feb. 20, 1990, column 1, beginning on line 26.
The basic disadvantage of the sit-up method of exercising the abdominal muscle group is that hip flexor muscles play a prominent role in this movement. A second disadvantage is that one must lie on the floor to perform the movement and the third disadvantage is that it is difficult to control or adjust the resistance. There are a number of "special purpose" devices currently on the market advertised to exercise the abdominal muscle group. As to many of these devices, there is a serious question as to whether they do strengthen the abdominal muscle group.
There are on the market today many legitimate devices sold for the express purpose of exercising the abdominal muscle group. There are such devices that do work the abdominal muscles and are available for the commercial gym as well as for home use. However, the disadvantage of these devices is the size of many of them as well as the cost.
Back injury and pain is the largest single musculo-skeletal problem affecting mankind. Expenditures in the neighborhood of one billion dollars are made in this country each year on back disorders.
The main reason for all of these low back problems in man is the strength imbalance between hip flexor muscles and the abdominal muscles. It is estimated that as much as 85% of all low back problems are due to weak abdominal muscles. There are two groups of muscles directly involved in performing such exercises as sit-ups and leg raises. They are the trunk flexors and hip flexors. The abdominal muscles attach to the front and sides of the rib cage and the pelvis; they do not cross the hip joint. A main purpose of these muscles is to stabilize the pelvis and chest so that other muscles can move the arms and legs or fix parts of the trunk in desired movements. The trunk flexors and hip flexors are not directly involved in the movements of the hips. Many persons perform various sit-ups and even weighted sit-ups in an effort to balance the development of the trunk flexors and the hip flexors. However, any abdominal exercise performed with the feet anchored with rollers or a strap is predominantly hip flexion, and the key factor is that it is TRUNK FLEXION that activates the abdominals.
Abdominal exercises which are predominantly hip flexion are undesirable for at least two reasons. First, the hip flexions are naturally seven times stronger than the abdominals, and further strengthening of these muscles can result in hip flexor-abdominal imbalance, manifested in an exaggerated anterior pelvic tilt and lumbar curve (lordosis). Second, since the abdominals are receiving minimal work, they cannot generate the force to counter the antagonistic erector spinae group which, when coupled with the strength and adaptive shortening of the hip flexors (which occurs as a result of the performance of an incorrect sit-up exercise) leads to a loss of structural integrity and to postural deviations.
In addition to the patent to Buoni, above identified, U.S. Pat. No. 4,867,445 granted to Connelly on Sept. 19, 1989, shows a resistance device for use in chairs. This device does not use the muscle groups for which this present invention was developed. The same can be said of U.S. Pat. No. 4,618,140 granted to Brown on Oct. 21, 1986.
U.S. Pat. No. 4,666,152 granted to Jones on May 19, 1987 shows a device for exercising the abdominal muscles but without utilizing the concepts of the present invention. The same can be said of U.S. Pat. No. 3,912,265 granted to Muir on Oct. 14, 1975.
The following U.S. Pat. Nos. were located during a patent search relative to the present invention; but are not believed to be pertinent to that invention: 4,834,364 granted to Gongwer et al on May 30, 1989; 4,824,105 granted to Goldenberg on Apr. 25, 1989; 4,807,873 granted to Naquin on Feb. 28, 1989; and 4,641,833 granted to Trethewey on Feb. 10, 1987.
What was needed before the present invention was a device to exercise the abdominal and lower back muscles without undue stress on lumbar and cervical spinal discs and without over-exercising the hip flexor muscles. Also needed was such a device which is a very inexpensive, easily portable so that the exerciser can actually carry the device conveniently on travel away from home base, and which can be very easily adjusted to provide additional resistance as the user develops additional strength through the exercising.